Adequacy of binary fluid and turbulator based natural circulation loop in parabolic trough collector

The natural circulation loop (NCL) is in the limelight due to its sustainable and reliable mechanism. It finds application mainly in nuclear and solar thermal power plants. However, the low flow rate of fluid within the loop and instability causes a hindrance to their widespread applications. Hence many instability restraining and heat transfer augmentation techniques have been studied, including the recent innovations viz. binary fluid and turbulators. In the present experimental study, a horizontal heater horizontal cooler loop is constructed, and its behaviour is compared with the Vijayan correlation. Later, the wire coil (pitch ratio = 4) effect is studied for the heat input range of 200 W to 600 W, which resulted in the heat transport efficiency improvement of 20% to 22% in the laminar region and 5% to 8% in other regimes with decreased mass flow rate as penalty. Even binary fluid (40% acetone + 60% water) influence is monitored separately for the same heat input range. The loop was neutrally stable for 200 W to 500 W heat input, and at 600 W, pulsation of loop fluid flow with high magnitude was noticed. Though binary fluid enhanced the mass flow rate, the heat transfer rate was not improved due to acetone’s low specific heat value.